I will execute a big query so i want to know what is the maximum length of a mongodb query ?
The maximum size of a document, which is what you are constructing when you create a query is 16MB. You can see that, and other limits here:
http://docs.mongodb.org/manual/reference/limits/
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I cannot find the answer to this seemingly basic question. The documentation says the max size for a BSON document is 16MB.
I want to know what is the max size of a query result allowed. E.g., if there are 1,000 records in a collection, and each document is 1MB, will mongodb throw an error if there are 400 documents (totaling to 400MB)?
My sample use case is to Query data about people who have not blocked the user
and there is no limit to the number of people that can block the user
So my query looks something like
db.collection().find( { followedPersonId: { $nin: [ blockerId1, blockerId2, blockerId3.....] } } )
So the number of Array items in the $nin operator can grow to a potentially large number, So is there a limit to the size of this array in MongoDB?
The command size limit is currently set at 48 MB. If your query is bigger than that the driver should fail when trying to serialize it, and the server should fail if it was asked to parse it.
Since your query is technically a query document, I imagine the lower 16 MB BSON document size limit would also apply to it. The 48 MB limit applies to find-and-modify queries that specify a query document and an update document.
Short answer is NO!
When you try to do this the query will become huge. And performance will be less.
Will the ids be in crores?
If yes then I will suggest not to go with this method.
I am using mongodb for one of my application.
We are fetching large amount of records from the db.
We are facing following issue when we fetch large number of documents from db.
aggregation result exceeds maximum document size
Any option to set this max limit?
The documentation states that:
If you do not specify the cursor option or store the results in a
collection, the aggregate command returns a single BSON document that
contains a field with the result set. As such, the command will
produce an error if the total size of the result set exceeds the BSON
Document Size limit.
Earlier versions of the aggregate command can only return a single
BSON document that contains the result set and will produce an error
if the if the total size of the result set exceeds the BSON Document
Size limit.
The maximum BSON document size is 16 megabytes.
That actually is the problem that you have now.
Which is the limit of a mongodb array field?
subdocuments have a limit of 4mb-16mb(it depends of the version). Does an array has the same limits?
The only limit is the document size. Whatever Document (or ReferenceDocument) contains the array cannot exceed that size. See limits.
I'm using a mongodb capped collection which is tailable. I want to set the size of it to a maximum value as I don't want to really have the oldest records removed according to the FIFO rule.
I want the data to pesist for as long as possible whilst keeping the features of a capped collection.
Thanks
You can make the capped collection as big as you want; just set the size parameter of create_collection to a value big enough to not run out of space.
Like this:
db.create_collection('captest', capped=True, size=20000000000)
You can create the capped collection using size (in bytes), or max (maximum number of documents to keep), or both in this case:
pymongo ->
self.db.create_collection('system_health_log', capped=True, size=5242880, max=5000)
mongo shell ->
db.createCollection("system_health_log", { capped : true, size : 5242880, max : 5000 } )
See more here on Capped Collections.